Environmental pollution has become a serious problem not only in the United States, but also throughout the world. The combustion of fossil fuels to generate energy results in the exhaust gases containing harmful by-products of the combustion process. The exhaust gases contain small particulate matter remaining from the incomplete combustion of the fossil fuel. Typical exhaust gases contain nitrogen oxides, carbon monoxides, sulfur dioxides, carbon particulates, fly ash and magnesium sulfites.
Traditionally smokestacks of extended heights have been used to disperse the exhaust gases with the entrapped particulates directly into the atmosphere. This method achieved the desired result of relieving the area immediately adjoining the fossil fuel energy plant from the deleterious exhaust gases, but the exhaust gases and particulates were simply dispersed by the wind to the neighboring communities.
Eventually governmental restrictions, including the ability to impose substantial monetary fines, were enacted limiting the amount of particulates that could be emitted in the exhaust gases leaving the fossil fuel combustion apparatus. Many techniques have been proposed to control the particulate emission. Most prevalent is the use of an electrostatic precipitator (ESP) in the smokestack or other exhaust gas conduit.
However, one of the drawbacks of fitting a smokestack with an ESP is the large amount of energy that is required just to operate the ESP. ESP technology is also quite complicated and sensitive, requiring constant monitoring and close operational control to ensure that the ESP works correctly and effectively.
In current exhaust gas treatment technology, water is often sprayed into the exhaust gases prior to the beginning of the flow of the exhaust gases up the smokestack. This addition of water is used to try and scrub the particulates out of the exhaust gases. Typically, a bank of horizontal sprayers are disposed in a treatment chamber to spray the exhaust gases with either water or a water and lime mixture. This treatment chamber must be designed to include water sprays at the appropriate locations in the chamber and apparatus must also be included to collect the particulates removed from the exhaust gases as well as any excess water or lime from the process. Spraying water into the flow of the exhaust gases has not proven to be an efficient method of treatment because there is no way of ensuring that all of the particulates entrapped in the exhaust gases can be brought into contact with the water.
At least as early as 1911, it was proposed to take exhaust gases from a smelting furnace and force these gases through a body of water to precipitate and condense the volatile materials in the exhaust gas. Representative of such a proposal is U.S. Pat. No. 980,257 to Heslewood.
Heslewood discloses a fume condensing apparatus for use with a smelting furnace A. A series of exhaust vents 5 are disposed around the upper end of the furnace and the exhaust vents are connected by a manifold assembly 6 to an exhaust line 6'. The exhaust line 6' terminates in a bell-shaped suction chamber 7. A pump 14 has a nozzle 9 that also feeds into the suction chamber 7. A contracted throat 10 exits the suction chamber and is connected to a perforated pipe 12 that is disposed at the lower end of a tank 11 containing water.
In operation, Heslewood's apparatus withdraws water from the tank 11 and forces it at high pressure and velocity through the nozzle 9. The water passes through the suction chamber 7 and into the contracted throat 10 which creates a vacuum in the suction chamber 7. This vacuum draws gases and fumes from the smelting furnace A through the exhaust vents 5, through the manifold assembly 6 and exhaust line 6' into the suction chamber 7. The gases and fumes eventually are distributed by the perforated pipe 12 into the water in the tank 11. The water causes the gases and fumes to cool and condense. Precipitates fall to the bottom of the tank 11 where they may be collected and subsequently removed.
The Heslewood apparatus does not efficiently mix the intake water with the gases and fumes withdrawn from the smelting furnace. The gases and fumes injected into the water tank are not dispersed throughout the entire water body but rather are centralized in the water immediately adjacent the perforated pipe. The perforated pipe also has the tendency to become clogged thereby inhibiting the efficiency of the apparatus. The resulting exhaust gases that bubble up through the water in the tank may still contain harmful contaminants that are released into the atmosphere.
It is an object of the present invention to provide an exhaust gases and particulate capture system that simply and efficiently removes particulate matter from exhaust gases.
It is a feature of the present invention to utilize a highly efficient aspirator to mix exhaust gases with water and to pump this mixture at high speed into a tank of water where the particulates can precipitate and collect on the bottom of the tank. A positive pressure is maintained above the water level to prevent contaminated gases from escaping. Baffles are provided to quiet the turbulent water flow in the tank and a secondary screening tower is provided to clean the exhaust gases prior to these gases being vented to the atmosphere.
It is an advantage of the present invention that exhaust gases from furnaces can be cleaned of particulates and other harmful contaminants in an efficient and inexpensive manner at a cost significantly less than is incurred from the use of modern electrostatic precipitators.